The right ratio produces some x-factor.

What ratio of masses of black holes produces the maximum kick?

Different ratios can produce different effects.

Average mine price: The ratio of the total value of the coal produced at the mine to the total production tonnage.

Sarah Lawrence's female-to-male ratio of 3 to 1 produces, even for the men, a peculiar social environment.

Produces deep, true blacks allowing for superior contrast ratios (up to 1:1,000,000)

A ratio of one male to three females per cage will usually produce the best results in the majority of strains.

Other ratios produce less desirable finishes.

The ratio of fusion power produced to x-ray radiation lost to walls is an important figure of merit.

Other ratios produce more complicated curves, which are closed only if a/b is rational.